Preserve triangles at the interface between tetrahedra

Hi all,
I’m using mmg3d and need to preserve triangles at the interface between tetrahedra in some domain areas.

e.g., I would like to preserve the green surface in the images:

(both outside and inside the volume delimited by the green surface are present tetrahedrons)

Reading the documentation, the -opnbdy parameter seems to do exactly what I need.
Unfortunately, after the remeshing procedure, the surface is not preserved. Surely I’m doing something wrong but I don’t know what.

Could I get an example of how to use the -opnbdy parameter?
Or, if there is another way to do what I need.

I really appreciate any help you can provide.


Ni Nicola,

I have added a very short tutorial on the Mmg website (Open boundary remeshing – Mmg Platform).

The opnbdy option is useful to avoid the deletion of internal pieces of surfaces by Mmg (by pieces of surfaces, I mean open surfaces inside the volume that don’t delimit a domain). Normally, when you use the opnbdy option, internal pieces of surfaces are keeped and remeshed at the same time that the volume.

If you also want to forbid the remeshing of these surfaces, you will have to mark the input triangles as required before calling Mmg or to use the -nosurf option if you forbid the remeshing on all boundaries.

Best Regards,